The Long Plug Flow Furnace LPFF Model

The computed flux densities are nearly equal because there is asingle sink zone Aj. 

Input/Output Performance Parameters for Furnace Operation The term firing density is typically used to define the basic operational input parameter for fuel-fired furnaces. In practice, firing density is often defined as the input fuel feed rate per unit area (or volume) of furnace heat-transfer surface. Thus defined, the firing density is a dimensional quantity. Since the feed enthalpy rate Hf is 

The LPFF model is described by only two dimensionless parameters, namely an effective firing density and a dimensionless sink temperature, viz., 

Here the dimensionless firing density, NFD, and a dimensionless convection-radiation namber 1VCR are defined as 

In analogy with a conventional heat exchanger, Eq. (5-178) displays two asymptotic limits. First define 

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The Long Plug Flow Furnace (LPFF) Model. 5-39... 

Note The long plug flow furnace Model is so efficient that it would be grossly underfired using the computed WSCC effective firing density. Of the two models, the LPFF model always predicts an upper theoretical performance limit. 

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